It may be desirable to vent fuel tanks to reduce pressure therein to reduce the likelihood of overpressure conditions in the fuel tank. Venting the fuel tank may include flowing air/vapors to a fuel vapor canister and/or venting fuel vapors via a fuel cap. In the case of plug in hybrid vehicles, the internal combustion engine may not operate for a prolonged period of time. In such systems, the fuel tank are sealed and can reach high pressures, necessitating additional venting operation and further exacerbating the aforementioned problem of fuel tank over-pressurization. Fuel tank sensors may be used as an indicator for venting operation. Venting operation may rely upon pressure sensors positioned in the fuel tank. The pressure sensors in the vehicle's fuel tank can fail, leading to problems such as fuel tank over-pressurization and subsequent fuel tank degradation and in some case failure.
The inventors herein have recognized an issue with the above type of systems and developed a method for operating a vehicle system. The method includes monitoring a change in a temperature of the fuel vapor canister coupled to a fuel tank via a canister temperature sensor and adjusting operation of a fuel tank isolation valve based on the change in temperature of the fuel vapor canister. It will be appreciated that the change in temperature of the fuel vapor canister can be correlated to a fuel tank pressure. This correlation can be useful when a fuel tank pressure sensor is degraded. Therefore, the aforementioned method may be implemented subsequent to fuel tank pressure sensor degradation, in one example. Consequently, venting operation, implemented via opening and closing of the fuel tank isolation valve, can rely upon multiple sensors (i.e., a fuel tank pressure sensor as well as a fuel vapor canister temperature sensor), increasing the reliability of and improving venting operation in the vehicle system. In another example, the monitored change in temperature of the fuel vapor canister can be used to determine fuel tank pressure sensor functionality. In this way, the temperature sensor can also be used to improve fuel tank pressure sensor diagnostics.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.